Climbing Power Equation: how to make a calculation into usable code

I'm trying to write a specific equation that includes derivation. This specifically:

The data I am looking at is from three cameras focused on a flying bird. after running the position data through some smoothing functions its derived to get velocity and acceleration.

So I'm working with the velocities in the X,Y, and Z directions in an excel file (aDdatafilt1).

Heres what I have so far but I don't think Im using diff() correctly:

%GENERATE CLIMB POWER FOR BIRD "A"
XVel=aDdatafilt1(:,1);
YVel=aDdatafilt1(:,2);
ZPos=aDdata(:,3);    % aDdata = position data

t=[1/60] ;    %fps of cams = 60
XYVel=sqrt(XVel.^2+YVel.^2);
Pkmt=(.5.*abs(XYVel).^2+(9.8)*(ZPos));
Pkm = diff(Pkmt,t) 

Thanks.

Answer 1

[Rohit Pappu]

To calculate the first derivative of a particular vector X, the syntax is diff(X,1)

For the above equation,

Pkm = diff(Pkmt,1)/t 

is equivalent to

[Robert J Hanna]

Thank you! that worked